144 0001795151 XXXXXXXX LIVE 0001708035 ECOVYST INC. 001-38221 600 Lee Road, Suite 200 Wayne, PA 19087 (484) 617-1200 Susan Ward Director Common Morgan Stanley Smith Barney LLC Executive Financial Services

1 New York Plaza 8th Floor New York NY 10004

15000 126016.50 114019414 11/07/2025 NYSE Common 01/05/2022 Restricted Stock Issuer N 12995 01/05/2022 Not Applicable Common 01/05/2024 Restricted Stock Issuer N 2005 01/05/2024 Not Applicable Y 11/07/2025 /s/ Susan Fitzgerald Ward